The long term objective of this research is to determine what brain systems regulate female sexual behavior in the mammal. Since the brain systems which regulate sexual behavior are themselves influenced by gonadal hormones as well as a variety of drugs, it is important that we understand how these systems operate. The present research program utilizes chemical stimulation of the brain and a variety of assays to determine what kinds of neurological systems mediate female reproductive behavior. These studies, utilizing laboratory rats, will provide insight into the mechanisms by which ovarian hormones affect the brain and behavior. Such information will form the necessary basis for understanding the neural bases of sex differences in motivation and behavior.